Mechanical adjusting arrangement

ABSTRACT

Mechanical adjusting arrangement, in particular for braking members in motor vehicles, which are operated by means of a selfbraking or non-reversible outer thread set or a pair of cooperating curved cam elements corresponding thereto for adjusting an abutment, there being a reversible central and coaxial inner thread set or curved pair of elements, one thread of each of the two thread sets being disposed upon the same rotatable spindle, the two thread sets having the same lead and being of the same hand. The outer thread set also serves to support the rotatable spindle; the inner, central thread set is freely mounted and is used to drive the rotatable spindle. In the disclosed embodiment the outer thread set is composed of a thread on a brake-operating piston mounted for axial reciprocation and held from rotation about its longitudinal axis, the other thread of such set being that on the outer surface of the adjusting spindle.

United States Patent 1 Baezold [451 Sept. 11, 1973 1 1 MECHANICALADJUSTING ARRANGEMENT [76] lnventor: Karl Baezold, Niederbarnstrasse 13,

Frankfurt am Main, Germany [22] Filed: Dec. 21, 1970 [21] Appl. No.:100,209

[52] U.S. Cl. 188/196 D, 188/719 [51] Int. Cl. Fl6d 65/56 [58.] Field ofSearch l88/7l.8, 71.9, 79.5 GE, 188/196 D, 196 F [56] References CitedUNITED STATES PATENTS 2,949,173 8/1960 Peras 188/196 D 3,244,260 4/1966Frayer 188/196 D Primary ExaminerDuane A.'Reger Attorney--Arthur O.Klein [57] ABSTRACT same lead and being of the same hand. The outerthread set also serves to support the rotatable spindle; the inner,central thread set is freely mounted and is used to drive the rotatablespindle. 1n the disclosed embodiment the outer thread set is composed ofa thread on a brake-operating piston mounted for axial reciprocation andheld from rotation about its longitudinal axis, the other thread of suchset being that on the outer surface of the adjusting spindle.

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.1 MECHANICAL ADJUSTING ARRANGEMENT This invention relates to amechanical adjusting mechanism, and more particularly a mechanism usefulto render brakes, such as automotive disc brakes, selfadjusting. In suchself-adjusting mechanisms for brakes, there is usually an abutment meanswhich is adjusted as required to compensate for the wearing of a brakeshoe.

In one prior self-adjusting mechanism for brakes, which is provided witha steep thread, there is sometimes slippage of the nut on the threadwhen the brakes are applied, such slippage being in the directionopposite from the direction of motion of the brake shoe. In those caseswhere such slippage of the nut along the screw is prevented, as by meansof the provision of conical bearing surfaces which are forcibly moved,there may occur a small elastic deformation of the parts forming theabutment for the brake shoe operating mechanism, in view of the largeforces to which such elements are subjected.

In another known mechanism for the self-adjustment of brakes, there areemployed self-braking threaded spindles, adjustably driven by a rotarydriving means. In practice, because of the wear imposed upon them, theself-braking thread spindles must be readily replaceable. In suchconstructions there have been provided a self-braking spindle with a camguide means which is coaxial of the spindle and which is turned tofollow the movement of the spindle. The resulting adjusting path,because of inherent limitations of space, is substantially smaller thanthe instantaneous amount of wear of the brake shoe. Since the amount ofwear of the brake shoe is small, the resulting adjustment of theadjusting mechanism is still smaller; this requires the entireconstruction of the brake and the self-adjusting mechanism to beextremely precise, in order to provide a correct brake-adjustingfunction. Of course, with such necessary increased precision, thepossibility of the malfunctioning of the brake and its parts isincreased. Due to these facts, the manufacture of this type ofself-adjusting brake is no longer economically feasible.

In the mechanical self-adjusting arrangement in accordance with thepresent invention, there is employed a radially outer, self-brakingthread set or a corresponding set of helical guide means, the drive forthe adjusting means being a centrally arranged reversible thread set ora corresponding set of cooperating curved guide means. The inventionmakes use of the fact that the limits of the self-braking or theirreversibility of the outer thread or curved guide set is not dependentupon the lead (pitch x thread number), but are dependent upon the pitchangle, which means that with identical values of lead with sufficientlylarge differences in diumeter a thread set or a curved guide set can beat one time absolutely irreversible or self-braking and on the otherhand can be easily free turning. From these considerations, it can beseen that a thread set or curved guide set with a smaller diameter atthe centralaxis of the braking piston, when fixedly connected to thefront face of the piston, can be used as a very simple driving means fora coaxial rotatable threaded element on which the brake piston issupported. One must take care, however, that during .the adjustingmovement all of the flanks of the larger coaxial supporting thread setor curved guide set are moved out of engagement with each other and arepost-turned without friction, be-

cause otherwise, due to the larger friction radius, there could arise avery substantial opposing torque.

The outer thread set of the coaxial support has, at all times, largethread flanks, such outer thread set being preferably formed as a singlethread. The inner thread set, which drives the adjusting means, ispreferably made as a plural or multiple thread. This, however, is

' simply accomplished in practice, and so there results no markedincrease in fabrication costs or other difficulties. The construction ofthe threads in the two thread'sets should, as a matter of practice, beas simple as possible; all types of known and suitable thread forms canbe used, such as, for example, pointed, flat, trapezoidal types ofthreads, and similar threads, the types of threads and curvedconfigurations which are combined with each other depending upon the useto which the arrangement is to be put.

The complete adjusting arrangement, therefore, consists only of twothread sets or curved element pairs, wherein the one that is smaller indiameter at all times drives the larger one to adjust it. By means ofsuch pairing of thread sets or curved guide elements, there are avoidedthe radially directed high-force components which occur in a steepthread support, which require a strong construction with a large amountof material, and cause an elastic deformation of the parts. Thus, withthe leadof the central drive thread set being the same as that of theouter thread set, the adjustment effected always amounts to the entireamount of wear of the brake shoe; this is particularly advantageous incases of high rates of wear of the brake shoes,'or after a brake shoechange. In addition, this makes themechanical sensitivity of thearrangement insignificant. The construction of the mechanism inaccordance with the invention is exceedingly strong and simple. Theadjustment'of the space between the face of the brake shoe and the brakedisc or drum can be easily effected by turning one of the members of thepair of threaded elements carrying the 'outer and inner thread sets.

In the accompanying drawings which form a part of the specification:

FIG. 1 is a view partially in longitudinal axial section and partiallyinside elevation of a first embodiment of self-adjusting brake mechanismin accordance with the invention, such device having a central or innermultiple thread set and an outer coaxial single thread set, such threadsets having the same lead and being of opposite hand;

FIG. 2 is a view partially in longitudinal axial section and partiallyin side elevation of a second embodiment of self-adjusting brakemechanism in accordance with the invention, such mechanism havingacentral steep set of curved guiding means, and a second, radially outercoaxial set of curved guiding means, the two sets of curved guidingmeans having the same pitch but being of opposite hand;

FIG. 3 is a fragmentary schematic view in radial longitudinal sectionthrough a left piston and housing of a mechanism similar to that of FIG.1, the piston being shown retracted to the left into its brake offposition;

FIG. '4 is a view similar to FIG. 3 but with the piston having beenadvanced to the right through a distance a in a normal brake-applyingstroke; and

FIG. 5 is a view similar to FIG. 4 but with the piston having beenadvanced to the right through a distance 3 12 thereby adjusting theposition of the shaft by engaging It.

In FIG. 1 there are shown two oppositely disposed coaxial housings l2,13 which form the cylinders of the braking mechanism. Such housings aresupported upon fixed structure, not shown. Mounted in housings 12 and 12respectively are pistons 6 and 15 which, upon the introduction of fluidunder pressure into the rear ends of the cylinders through conduits 11and 11a move inwardly toward each other. Fixedly connected to the inner,opposing ends of the respective pistons are disclike brake shoe carriersand 10, respectively upon which there are fixedly secured the brakeshoes 9 as shown. The inner ends of the brake shoes 9 confront theopposite annular braking surfaces of the thickened edge portion 45 of abrake disc 46. The distances between the inner, braking surfaces of themembers 9 and the surfaces of the portion 45 of the brake disc areexaggerated in FIG. 1 for clarity of illustration.

Means are provided for constantly urging the pistons 6 and into theirouter, retracted positions; such means is shown in FIG. 1 as being acoil compression spring 8 which is compressively held between springseats provided on radial extensions 10a on the brake shoe mountingmembers 10 and 10.

Considering now the housing 12 andthe piston 6 thereof at the left inFIG. 1, there is an adjusting spindle 5 which is mounted coaxial of thehousing 12 and of the piston 6. Spindle 5 is in the form of a cup openat its right end, the left end of the cup having a stub shaft integraltherewith extending to the left and coaxially thereof. Such stub shaft,which is sealed to the housing 12 by an O-ring 4, is flanged at itsouter end, there being two opposed shallowly dished spring rings 2compressively retained between the flange on the end of the stub shaftand a plastic sealing ring 3 in housing 12 which surrounds the stubshaft. A key or wrenchreceiving formation on the outer end of the stubshaft beyond the flange is covered by a removable elastic protectivecap 1. The described arrangement retains the spindle 5 in its left handposition abutting the left hand end of the inner wall of the housing 12,but permits its rotation, for adjustmentof the inner, retracted endposition of the piston 6, upon the removal of the protective cap 1 andthe insertion of a suitable key or wrench into the formation on the endof the stub shaft, thereby turning the spindle 5.

A drive spindle or shaft 7, coaxial of the housing 12, the piston 6, andthe adjusting spindle 5, has its right hand end press fitted into theforward or right hand face of the piston 6 so that the drive piston 7 isfixedly, non-rotatably mounted upon piston 6. The inner wall of thepiston 6, which is of cup-shape and open to the left, is internallythreaded, the outer periphery of the adjusting spindle 5 beingcorrespondingly threaded, whereby to form a first, outer thread set 5a.The inner wall of the adjusting spindle 5 is threaded, such threadedinner wall receiving the threaded outer surface of the drive spindle 7;such latter two threads form the second, inner thread set 512.

As above-described, and shown more clearly in FIGS. 3, 4, and 5, to bediscussed below, the first, outer thread set 5a has a single thread. Thesecond, inner thread set 5b is a multiple thread, in this case havingtwo threads. Thread sets 5a and 5b have the same lead (pitch x threadnumber and are of the same hand. Thread set 5a is irreversible orself-braking, whereas thread set 5b is reversible under forcesencountered when the parts are in the relative positions shown in FIG.5.

The parts of the brake shown at the right in FIG. 1 are generallysimilar to those above-discussed found in the portion of the brake atthe left. The reference character l3 designates a sealing ring, 14 is adrive spindle, 15 is a right hand brake piston, 16 is an adjustingspindle, 17 is a sealing ring, and 18 is a plastic ring. In thisinstance there are employed two dish-shaped rings, here designated 19,which are used in tandem. Such springs 19, which bear against theplastic ring 18, cause the return of a swingable hand brakemotiontransmitting lever 21 pivoted on a fixed structure of the brake bya pivot pin 20. The upper end of the lever 21 is surrounded by aremovable plastic protective cover 22.

The manner of operation of the self-adjusting brake mechanism shown inFIG. 1 and above-described will be clear from a consideration of FIGS.3, 4, and 5. In FIG. 3, the piston 6 is shown as having been pushed tothe left by the spring 8 into its left hand terminal position in whichthe left hand flanks of the threads on the inner wall of the piston 6are in abutting engagement with the right hand flanks of the threads onthe periphery of the adjusting spindle 5. In such position, the flanksof the threads making up the thread set 5b are somewhat spaced, asshown. In the retracted position of the piston 6 shown in FIG. 3 thereis a predetermined minimum spacing between the left hand end of thepiston 6 and the confronting end wall of the housing 12. Such spacepermits the introduction of brake fluid under pressure through theconduit 11a to act upon the left hand end of the piston when the brakesare applied.

FIG. 4 shows the relative position of the parts upon the application ofthe brakes in a normal braking operation. Braking fluid under pressurehas now been introduced into the cylinder through the conduit 11a. As aresult, the piston 6 has been thrust to the right through a distance aso as to apply the inner face of the brake shoe 9 to the left hand faceof the brake disc portion 45. In such position of the parts, the flanksof the two threads forming the thread set 5a are spaced. This is alsotrue of the flanks of the threads forming the inner thread set 5b. Thus,the arrangement shown allows the free reciprocation of the piston 6 in anormal braking operation through the distance a without causing theoperation of the adjustable spindle 5.

In FIG. 5, it is assumed that the brake shoe 9 has worn to such anextent that further travel b of the piston 6 is required in order toapply the brake shoe to the brake disc in a normal braking operation. Insuch condition, the right hand flanks of the radially outer threadforming the thread set 5b engage the left hand flanks of the radiallyinner thread of such set. Because of the reversability of the thread set5b, the adjusting spindle 5 is turned by such action of the thread set5b so that the outer thread set 5a will now permit the required travelof the piston 6 to the right. At the same time, because of the rotationof the adjusting spindle 5, when the brake is released by ceasing theapplication of brake fluid under pressure through the conduit 110, thepiston 6 returns to its left hand retracted position in which thethreads of the thread set 5a have the relative positions shown in FIG. 3but the piston 6 now lies at a position which is further to the right bythe distance b than it was in FIG. 3, Thus, the inner, braking surfaceof the brake shoe 9 is always maintained at a predetermined distancefrom the surface of the brake disc when the brake shoe is in itsretracted position.

The construction shown in FIG. 2 is generally the same as that shown inFIG. 1 with the exception that for the radially inner and outer threadsets 5a and 5b of FIG. 1 there have been substituted, respectively, aninner curved guide in the form of a cam 30a on the drive spindle and acam follower 29 on the adjusting spindle, and curved guide surfaces, ofa hand opposite from that of the cam 30a, on the interior of the pistonand the exterior of the adjusting spindle. Such radially outer curvedsurfaces are designated 39a and 40a in FIG. 2.

A plastic protective cap 23 covers the spindle end which bears thedish-shaped spring 24. Ball bearings 26 roll around a supporting ring orrace 25, thus to reduce the friction which is caused by the action ofthe dishshaped springs at the bottom of the housing. The elastic ring 27seals off the projecting end of the adjusting spindle 28. The guideshaft 29 has a pressed fixed connection with the adjusting spindle 28;the guide shaft 29 projects into a guide groove 30a disposed in thedrive spindle 30. The drive spindle 30 is fixedly pressed and held inthe left brake piston 32. Brake sealing rings 35 are mounted in thebrake member housing 34. A brake member 36 is mounted on the brakesupport 37. The drive spindle 38 is fixedly mounted upon the rightpiston 39. The dish-shaped springs 41 are mounted on the shaft end ofthe adjusting spindle 40. The hand brake transmission lever 43 ispivotally mounted by means of a pivot pin 42. A protective cover 44surrounds the upper end of the lever 43. I

When the brake pistons 32 and 39 are subjected to a hydraulic pressurethrough the conduits 33a and 33, the curved surfaces 39a and 40a,associated with the adjusting spindles 28 and 40, are disengaged andsimultaneously push the guide member 29 in the drive spindles 30 and 38against the guide shaft 29, whereby the adjusting spindles are turnedthrough a corresponding angle to maintain the air gap or space betweenthe inner face of the retracted brake shoe and the brake disc of thesame magnitude. The adjusting spindles 28 and 40 can be suitably turnedto adjust the retracted position of the brake shoes, upon removing theprotective caps 23 and 44 and applying a suitable tool to the nowexposed outer ends of such spindles.

The mechanical adjusting arrangement in 'accordance with the inventioncan be incorporated as a part of a protective return push means intohydraulic or exclusively mechanical drive systems. included in suchsystems are, for example, hydraulic cyl inders,freely supportedspindles,or the like. In the arrangement'of ous modifications within thescope of the appended claims.

What is claimed is:

l. A mechanical arrangement for adjusting an abutment means foralongitudinally reciprocable member, said member having first and secondsurfaces of substantially different diameter coaxial of the axis ofreciprocation of the member, an abutment adjusting spindle having thirdand fourth surfaces confronting the said first and second surfaces,respectively, a first helical guide set formed by cooperatingconfronting guides on the first and third surfaces, and a second helicalguide se't formed by cooperating confronting guides on the second andfourth surfaces, the first helical guide set constituting said abutmentmeans and being irreversible under longitudinally directed forces, andthe sec ond helical guide set being reversible under longitudinallydirected forces, whereby longitudinal movement of the member in excessof that taking up the play in the second guide set rotates the spindleto change the engagement between the guides of the first guide set.

2. An arrangement according to claim 1, wherein the helical guide setshavethe same lead and are of the same hand.

3. An arrangement according to claim 1, wherein the helical guide setsare composed of interengaging coopwhich is coaxial of the first cup andis reversely positioned longitudinally from the first cup, the guidesforming the first and second helical guide 'sets being disposed on theconfronting walls of the two cups, and on the inner wall of the secondcup and the central drive spindle, respectively.

5. An arrangement according to claim 1, comprising means independentlyto adjust said abutment means by turning said abutment adjustingspindle.

6. An arrangement according to claim 5, wherein said independentadjusting means comprises a central shaft connected to and extendingaxially from the abutment adjusting spindle.

7. An arrangement according to claim 4, wherein said independentadjusting means comprises a central shaft connected to and extendingaxially from the closed end of the'second cup forming the body of theabutment adjusting spindle, and means on said shaft whereby it and theadjusting spindle may be turned manually.

8. An arrangement according to claim 7, comprising a fixed housingenclosing said arrangement, said housing having a transverse wallthrough which said shaft extends and in which it is journ'alled.

" 9. An arrangement according to claim 1, comprising yieldable meansconstantly urging the reciprocable member in one axial direction, andmeans which overcomes the yieldable means to thrust the reciprocablemember in the opposite axial direction.

it is in no way limited to the disclosure of such a plurality ofpreferred embodiments, but is capable of numer- 10. An arrangementaccording to claim 9, comprising a fixed housing enclosingthearrangement, a cylinder within the housing, the reciprocable memberbeing a piston mounted in said cylinder, and means selectively toconduct fluid under pressure to the space rearwardly of the firsthelical guide set can be changed as needed by means of a rotationalmovement of one of the elements carrying at least one of said helicalguides.

13. A mechanical adjusting arrangement according to claim 12, comprisingmeans connected to said abutment adjusting spindle whereby it may berotated manually to change said locking and support directions.

1. A mechanical arrangement for adjusting an abutment means for alongitudinally reciprocable member, said member having first and secondsurfaces of substantially different diameter coaxial of the axis ofreciprocation of the member, an abutment adjusting spindle having thirdand fourth surfaces confronting the said first and second surfaces,respectively, a first helical guide set formed by cooperatingconfronting guides on the first and third surfaces, and a second helicalguide set formed by cooperating confronting guides on the second andfourth surfaces, the first helical guide set constituting said abutmentmeans and being irreversible under longitudinally directed forces, andthe second helical guide set being reversible under longitudinallydirected forces, whereby longitudinal movement of the member in excessof that taking up the play in the second guide set rotatEs the spindleto change the engagement between the guides of the first guide set. 2.An arrangement according to claim 1, wherein the helical guide sets havethe same lead and are of the same hand.
 3. An arrangement according toclaim 1, wherein the helical guide sets are composed of interengagingcooperating threads.
 4. An arrangement according to claim 1, wherein thereciprocable member has a main body in the form of a first cup, andcomprising a central drive spindle fixedly secured to said main bodycoaxial thereof, and wherein the adjusting spindle is in the form of asecond cup which is coaxial of the first cup and is reversely positionedlongitudinally from the first cup, the guides forming the first andsecond helical guide sets being disposed on the confronting walls of thetwo cups, and on the inner wall of the second cup and the central drivespindle, respectively.
 5. An arrangement according to claim 1,comprising means independently to adjust said abutment means by turningsaid abutment adjusting spindle.
 6. An arrangement according to claim 5,wherein said independent adjusting means comprises a central shaftconnected to and extending axially from the abutment adjusting spindle.7. An arrangement according to claim 4, wherein said independentadjusting means comprises a central shaft connected to and extendingaxially from the closed end of the second cup forming the body of theabutment adjusting spindle, and means on said shaft whereby it and theadjusting spindle may be turned manually.
 8. An arrangement according toclaim 7, comprising a fixed housing enclosing said arrangement, saidhousing having a transverse wall through which said shaft extends and inwhich it is journalled.
 9. An arrangement according to claim 1,comprising yieldable means constantly urging the reciprocable member inone axial direction, and means which overcomes the yieldable means tothrust the reciprocable member in the opposite axial direction.
 10. Anarrangement according to claim 9, comprising a fixed housing enclosingthe arrangement, a cylinder within the housing, the reciprocable memberbeing a piston mounted in said cylinder, and means selectively toconduct fluid under pressure to the space rearwardly of the piston inthe cylinder to thrust the piston in said opposite axial direction. 11.An arrangement according to claim 1, comprising a rotatable brakingelement, and a brake shoe mounted on the reciprocable member andselectively thrust thereby into operative braking engagement with thebraking element.
 12. A mechanical adjusting arrangement according toclaim 1, wherein the locking and support directions of the first helicalguide set can be changed as needed by means of a rotational movement ofone of the elements carrying at least one of said helical guides.
 13. Amechanical adjusting arrangement according to claim 12, comprising meansconnected to said abutment adjusting spindle whereby it may be rotatedmanually to change said locking and support directions.